The present invention relates in general to power control devices for pumps of the type having a delivery adjuster including an adjustment member, an adjustment spring acting on the adjustment member, a control piston exposed to pressure of the pumped medium and being biased by a governor spring exhibiting a progressive characteristic of its spring force. In a prior art power control device of the afore-described type to change the normally constant power output (product of the amount of the delivered medium and of pressure of the medium) of the adjustable pump the governor spring has to be changed. Such replacement however is usually a cumbersome operation.